Tillskottsvatten i avloppsledningsnät medför stora kostnader i form av underhåll,ökad mängd kemikalier och energi som även belastar miljön. Syftet med detta examensarbetevar att få ökad förståelse av temperaturförhållanden mellan spillvattenoch mark för att förbättra modelleringen av tillskottsvatten. Hypotesen är att spillvattentemperaturensjunker vid inläckage då temperaturen på tillskottsvattnet ärlägre än spillvattnet. Ett spillvattenrör med en längd på ungefär 2,5 km i Umeåundersöktes med givare jämt fördelade längs sträckan. Metoden innebar att medmätvärden på temperaturerna för spillvattnet, luften i spillvattenröret och i markentillsammans med flödet och nivån på spillvattnet modellera värmeutbytet i COMSOLMultiphysics. Resultatet gav fyra liknande funktioner för både spillvattenregionenoch luftregionen som beskrev värmeutbytet mellan spillvattenröret och marken.Effektutbytena hade en linjär tendens som funktion av temperaturdifferensen mellanspillvatten och mark under mätperioden fram till maj månad men med en högspridning då effektutbytet är även beroende på flödet och inte bara temperaturdifferensen.Majoriteten av effektutbytet var mellan ytan på spillvattenröret ochspillvattnet. I regionen mellan luft och yta på spillvattenröret så var majoriteten aveffektutbytet ifrån strålningsutbytet mellan spillvattnet och ytan. Resultaten gaväven U-värden för regionen mellan spillvattenregionen och luftregionen i rörledningenoch dessa var omkring 4 W/(m2K) respektive 0,8 W/(m2K). Tillskottsvattnetmodellerades utifrån värmeutbytet och det visade på ökade flödesnivåer när det varvåtperioder med en noggrannhet på ± 1 kg/s. / Supplemental water in the sewer network entails large costs in the form of maintenance,increased amounts of chemicals and energy that also have a burden on theenvironment. The purpose of this thesis was to gain an increased understandingof temperature conditions between wastewater and soil to improve the modelingof supplemental water. The hypothesis is that the waste water temperature dropswhen leakage occurs and when the temperature of the additional water is lower thanthe wastewater. A wastewater pipe with a length of approximately 2.5 km in Umeåwas examined with sensors evenly distributed along the path. The method involvedmodeling the heat flow in COMSOL Multiphysics with measured values of thetemperatures for the wastewater, the air in the wastewater pipe and in the groundtogether with the flow and the level of the wastewater. The result gave four similarfunctions for both the wastewater region and the air region that described the heattransfer from the wastewater pipe to the ground. The heating effects had a lineartendency as a function of the temperature difference between wastewater and soilduring the measurement period up to the month of May, but with a high spread asthe heat transfer is also dependent on the flow and not just the temperature difference.The majority of the heat transfer was between the surface of the wastewaterpipe and the wastewater. In the region between the air surface on the wastewaterpipe, the majority was the heat transfer from the radiation between the wastewaterand the surface. The results also gave U-values for the wastewater region and theair region in the pipeline and these were around 4 W/(m2K) and 0.8 W/(m2K),respectively. The supplemental water was modeled on the basis of the heat transferand it showed increased flow levels when it was wet periods with an accuracy of ±1 kg/s.

Doctor of Philosophy / Department of Chemistry / Takashi Ito / Self-organized nanoporous materials have drawn a lot of attention because the uniform, highly dense, and ordered cylindrical nanopores in these materials provide a unique platform for chemical separations and chemical sensing applications. Here, we explore self-organized nanopores of PS-b-PMMA diblock copolymer thin films and anodic gallium oxide for chemical separations and sensing applications. In the first study, cyclic voltammograms of cytochrome c on recessed nanodisk-array electrodes (RNEs) based on nanoporous films (11, 14 or 24 nm in average pore diameter; 30 nm thick) derived from polystyrene-poly(methylmethacrylate) diblock copolymers were measured. The faradic current of cytochrome c was observed on RNEs, indicating the penetration of cytochrome c (hydrodynamic diameter ≈ 4 nm) through the nanopores to the underlying electrodes. Compared to the 24-nm pores, the diffusion of cytochrome c molecules through the 11- and 14-nm pores suffered significantly larger hindrance. The results reported in this study will provide guidance in designing RNEs for size-based chemical sensing and also for controlled immobilization of biomolecules within nanoporous media for biosensors and bioreactors. In another study, conditions for the formation of self-organized nanopores of a metal oxide film were investigated. Self-organized nanopores aligned perpendicular to the film surface were obtained upon anodization of gallium films in ice-cooled 4 and 6 M aqueous H2SO4 at 10 V and 15 V. The average pore diameter was in the range of 18 ~ 40 nm, and the anodic gallium oxide was ca. 2 µm thick. In addition, anodic formation of self-organized nanopores was demonstrated for a solid gallium monolith incorporated at the end of a glass capillary. Nanoporous anodic oxide monoliths formed from a fusible metal will lead to future development of unique devices for chemical sensing and catalysis. In the final study, surface chemical property of self-organized nanoporous anodic gallium oxide is explored through potentiometric measurements. The nanoporous anodic and barrier layer gallium oxide structures showed slow potentiometric response only at acidic pH (≤ 4), in contrast to metallic gallium substrates that exhibited a positive potentiometric response to H⁺ over the pH range examined (3-10). The potentiometric response at acidic pH probably reflects some chemical processes between gallium oxide and HCl.

For this thesis, smart spraying robot was designed, constructed and tested to validate the concept of smart pest control. Electrostatic charging of sprayed pesticide was realized in a spray nozzle design that improved plant coverage and reduced wasted pesticide as well as soil pollution. A thorough investigation into electrostatic spraying was conducted, which was accompanied by extensive simulations and experimentation. The results obtained from the simulation experimentation on industry standard electrostatic spray system (ESS) nozzles along with laboratory testing of these nozzles, detecting spray coverage using water sensitive paper and additional optical spray visualization methods gave the necessary insight and experience required to develop a new spray nozzle. Additional COMSOL simulation and experimentation were carried out on a Fan Hydraulic Spray Nozzle (FHSN), the results of which allowed for the effective addition of electrostatic induction capabilities, thereby transforming the (FHSN) into Electrostatic Induction Spray Nozzle (EISN) which is one of the prime parts of the smart spraying system. SOLIDWORKS software was used in the designing parts of this nozzle which were then manufactured using a 3D printer. An AL05D robotic manipulator and a TTRK tracked platform from Lynxmotion ™ were the mini mobile robot components selected for the feasibility study of the smart electrostatic crop spraying system. This mobile robot was equipped with a CCD digital camera, a range detector, and path mark detector to provide the necessary sensors required by the smart electrostatic spray system. A Windows™ based mobile computer in addition to an ARDUINO™ based orksmicrocontroller system were chosen to provide the computational power required by the system. These were arranged in a master – slave configuration, with the main processing for images and motion being conducted inside the master computer using programs created by Matlab smart ™ software. The execution of motion commands and the operation of the range and path mark detection along with operating the spray nozzle were performed on the slave computer using C as the programming language. The manufactured smart electrostatic spray system moves along cotton crop rows with a camera that scans the selected plant for pest infestation on the upper and lower surfaces of plant leaves. When a pest is detected, the spray nozzle is targeted on it at the appropriate distance, and a burst of pesticide destroys it. The results of experiments have shown that using the electrostatic induction system improves coverage 3 to 4 fold and reduces soil contamination by 2 to 4 fold. The system has plenty of room for performance improvement, and future development will make it adaptable for application to other crops and applications.

The hydrogen economy is a possible component of an energy future based on use of alternative and renewable energy sources, deemed desirable from the general consensus of the worldwide community that we do not want to further exacerbate the climate problems that we have introduced over the last two centuries from burning fossil fuels. The burning of fossil fuels emits toxic pollutants into the air, such as sulfur compounds and oxidized forms of nitrogen (NOx) but also emit copious amounts of the inert carbon dioxide. The latter is widely recognized as the major cause of the global warming phenomenon. For a hydrogen economy to develop, efficient means of hydrogen generation are required. Thermochemical cycles were conceived in the 1960s but only one operating pilot plant and no commercial installations based on the processes have been built. In the present work the use of a membrane reactor to enable the newly conceived Sulfur-Sulfur cycle, based on equations 1 - 3 is modeled. / 4H₂O+4SO₂ -> H₂S + 3H₂SO₄ Eq. 1 / H₂SO₄ -> SO₂ + H₂O + 1/2O₂ Eq. 2 / H₂S + 2H₂O -> SO₂ + 3H₂ Eq. 3 / The rationale for the use of a membrane reactor to enable the cycle is based on enhancing extent of reaction beyond its predicted equilibrium point due to the severely unfavorable thermochemical parameters for the steam reforming of hydrogen sulfide reaction (Eq. 3 above) which has a low equilibrium concentration of products. The membrane reactor will employ a molybdenum sulfide catalyst driving the steam reformation of hydrogen sulfide reaction and simultaneous extraction of hydrogen (one of the products) will allowing for the reaction to occur to higher extent. A computational model of a catalytic membrane reactor was constructed using the well-known finite element model package Comsol v4.1 in which a catalytic microchannel reactor separated from a sweep gas by a thin hydrogen permeable membrane is built and parametric sweeps to evaluate the effect of membrane transport parameters, pressure and gas feed velocities are calculated. Though the steam reforming of hydrogen sulfide reaction has a competing thermal cracking reaction, the present work focuses on modeling one reaction only (the steam reformation reaction) for simplicity. Fully dense metallic membranes with chemselective permeability to hydrogen are modeled with transport parameters derived from reported literature values for similar applications. The results show that employing a membrane reactor does significantly affect the completeness of the reaction by product extraction (if you do run the model with membrane transport set to zero, compare the extent at zero with extent at 3.6x10⁻⁶ mol.s⁻¹.m⁻²). The effect of changing sweep gas velocity is contingent on membrane properties, and membranes with small diffusion coefficients severely limit the ability of extraction of hydrogen from the feed. Therefore, it is more important that membranes with very high hydrogen permeability be employed in designing a reactor to implement this process, allowing for effective hydrogen separation and high conversion of the reactants in the process. Reactor pressure has minimal effect on the extent of reaction and therefore reactors designed to implement the process may be designed to operate at close to ambient pressure. / Graduation date: 2012

Aluminium recycling requires 95% less energy than primary production with no loss of quality. The Black Dross (BD) produced during secondary aluminium production contains high amounts of water-soluble compounds, therefore it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results. The iron/steel industry is responsible for 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results, and where found to describe the results in a satisfying way. / <p>QC 20161128</p>

Poor heat and mass transfer inside the adsorbent bed of thermal wave adsorption cooling cycles cause low system performance and is an important problem in the adsorbent bed design. In this thesis, a new adsorbent bed is designed, constructed and tested to increase the heat and mass transfer in the adsorbent bed. The adsorbent bed is constructed from a finned tube in order to enhance the heat transfer. Additionally, the finned bed geometry is theoretically modeled and the model is solved time dependently by using Comsol Multiphysics software program. The distributions of dependent variables, i.e. temperature, pressure and amount adsorbed, are simulated and plotted in Comsol Multiphysics. In the model, the dependent variables are computed by solving the energy, mass and momentum transfer equations in a coupled way and their variations are investigated two-dimensionally. The results are presented with multicolored plots in a 2-D domain. Furthermore, a parametric study is carried out for determining factors that enhance the heat and mass transfer inside the adsorbent bed. In this parametric study, the effects of several design and operational parameters on the dependent variables are investigated. In the experimental study, the finned tube is tested using natural zeolite-water and silica gel-water working pairs. Temperature, pressure and amount adsorbed variations inside the adsorbent bed at various operating conditions are investigated. After that, a second adsorbent bed with a larger size is constructed and tested. The effect of the particle diameter of the adsorbent is also investigated. The experimental and theoretical results are compared.

Creating high resolution, or high-density, electrode arrays may be the key for improving cochlear implant users' speech perception in noise, comprehension of lexical languages, and music appreciation. Contemporary electrode arrays use multipolar stimulation techniques such as current steering (shifting the spread of neural excitation in between two physical electrodes) and current focusing (narrowing of the neural spread of excitation) to increase resolution and more specifically target the neural population. Another approach to increasing resolution incorporates microelectromechanical systems (MEMS) fabrication to create a thin film microelectrode (TFM) array with a series of high density electrodes. Validating the benefits of high density electrode arrays requires a systems-level approach. This hypothesis will be tested computationally via cochlea and auditory nerve simulations, and in vitro studies will provide structural proof-of-concept. By employing Rattay's activating function and entering it into Litvak's neural probability model, a first order estimation model was obtained of the auditory nerve's response to electrical stimulation. Two different stimulation scenarios were evaluated: current steering vs. a high density electrode and current focusing of contemporary electrodes vs. current focusing of high density electrodes. The results revealed that a high density electrode is more localized than current steering and requires less current. A second order estimation model was also created COMSOL, which provided the resulting potential and current flow when the electrodes were electrically stimulated. The structural tests were conducted to provide a proof of concept for the TFM arrays' ability to contour to the shape of the cochlea. The TFM arrays were integrated with a standard insertion platform (IP). In vitro tests were performed on human cadaver cochleae using the TFM/IP devices. Fluoroscopic images recorded the insertion, and post analysis 3D CT scans and histology were conducted on the specimens. Only three of the ten implanted TFM/IPs suffered severe delamination. This statistic for scala vestibuli excursion is not an outlier when compared to previous data recorded for contemporary cochlear electrode arrays.

Phase-change heat transfer is an important process used in many engineering thermal designs. Boiling is an important phase change phenomena as it is a common heat transfer process in many thermal systems. Phase change processes are critical to thermodynamic cycles as most closed loop systems have an evaporator, in which the phase change process occurs. There are many applications/processes in which engineers employ the advantages of boiling heat transfer, as they seek to improve heat transfer performance. Recent research efforts have experimentally shown that nanofluids can have significantly better heat transfer properties than those of the pure base fluids, such as water. The objective of this study is to improve the boiling curve of de-ionized water by adding aluminum oxide nanopthesiss in 0.1%, 0.2%, 0.3% and 0.4% wt concentrations in a sub-cooled pool boiling apparatus. Enhancement to the boiling curve can be quantified in two ways: (i) the similar heat fluxes of de-ionized water at smaller excess temperature, indicating similar quantity of heat removal at lower temperatures and (ii) greater heat fluxes than de-ionized water at similar excess temperatures indicating better heat transfer at similar excess temperatures. In the same fashion, the secondary objective is to increase the convective heat transfer coefficient due to boiling by adding different concentrations of aluminum oxide nanopthesiss.

L'objectif de ce travail est d'étudier expérimentalement la formation du capillaire durant le perçage et le soudage par faisceau laser, et de développer une simulation numérique permettant de reproduire la dynamique de formation et d'évolution du capillaire. Nous avons fait le choix d'utiliser comme matériau test le Zinc, en raison de ses propriétés thermodynamiques. Afin de simplifier le problème, nous avons étudié dans un premier temps le mécanisme de perçage. Deux méthodes expérimentales ont été utilisées pour caractériser l'évolution de la géométrie du capillaire : La méthode DODO (Direct Observation of Drilled hOle ) permet de visualiser le capillaire après perçage pour différentes durées et la méthode Zn-Quartz permet d'observer directement son évolution temporelle par camera rapide à travers une lame de quartz. Puis nous avons utilisé cette évolution pour mettre au point une simulation du mécanisme de perçage. Après avoir étudié le dépôt de puissance à l'intérieur d'un capillaire en tenant compte des réflexions multiples et estimé l'importance de la perte d'énergie et de matière lors du processus, nous avons développé une simulation en utilisant le logiciel Comsol Multiphysics couplant l'équation thermique, l'équation de Navier Stokes et prenant en compte le déplacement du métal fondu sous l'action de la pression de recul. Dans ce cas, on observe la formation d'un bourrelet important au bord du trou et une augmentation de la profondeur du capillaire. Ensuite nous avons étudié la formation du capillaire durant le soudage laser, c'est-à-dire avec déplacement de la source. A partir des techniques mises en œuvre pour l'étude du perçage nous avons obtenu l'évolution de la forme du capillaire dans le cas du soudage Zn/Quartz. Nous avons réalisé une simulation relativement simple en supposant la géométrie et la température du capillaire connues a priori. Nous avons constaté qu'un modèle simple, modélisant uniquement les transferts thermiques par conduction, permet de bien simuler la forme de la zone fondue pour les couples Zn/Zn et Zn-quartz.

The thesis deals with a computer modelling by means of the commercial software COMSOL Multiphysics. The thesis is structured into three topical sections. The first part is dedicated to the programme characteristics and its development. In the second part the brief characteristics of working with the programme COMSOL Multiphysics is presented which should make the user´s first steps in working with software easier. The last part of thesis shows the specific demonstration of the created multiple physics task taken from the field of plasma physics. This task is solved by means of continuous simulation of a computer modelling based on the drift-diffusion approximation of low temperature plasma. The proposal of the paper for the proceedings of the conference ,,Technical Computing Prague 2012" is also a part of this thesis.